There is a particular pleasure in spreading a map on the kitchen table the night before a walk. A mug of tea, a pencil, the faint crackle of paper that has been folded and unfolded a hundred times. This is slow living at its most useful, because an hour spent reading the map calmly at home saves a great deal of swearing at a gatepost in the rain. Learning a handful of symbols and habits will let you plan a route that suits your legs and your mood, rather than one that ambushes you with a climb you did not fancy.

Start with the footpath symbols

On British walking maps, the rights of way network is drawn in green. A green dashed line is almost always a public footpath — you on your own two feet, and nothing else. Add small crosses to those dashes and you have a bridleway, open to walkers, horse riders and cyclists. A line of green crosses marks a byway, where vehicles may legally travel, so expect ruts and mud. Long-distance trails are often picked out with an acorn symbol.

Black dashed lines are the ones to treat with care. They usually show paths that exist on the ground but carry no public right of way — permissive routes, farm tracks, or ways that can be closed on a whim. They are often perfectly lovely, but you need a plan B if a gate is locked or a sign says otherwise.

• Green dashes: public footpath, walkers only.
• Green dashes with crosses: bridleway, shared with horses and bikes.
• Green crosses: byway, expect vehicles and deep mud.
• Black dashes: unofficial or permissive, no guaranteed access.

Follow a green line with your finger and ask yourself where it actually goes. Paths that hug a field edge are usually clear on the ground. Paths that cut diagonally across the middle of a field are more likely to be ploughed out, faint, or invisible in tall crops.

Read the contours to judge the effort

Contour lines are the quiet workhorses of route planning. Each line joins points of equal height, and on most British maps they sit at 5 or 10 metre intervals. Lines close together mean steep ground. Lines far apart mean gentle ground. Count them to work out a climb: five lines at 10 metres is a 50 metre rise, which on a warm day you will feel in your calves.

Look at the shape, not just the number. Tight, evenly spaced lines rising in a smooth curve suggest a steady pull. Lines that bunch into a cluster then relax suggest a short, sharp sting followed by a plateau. Where a stream runs down between two sets of contours, you have a valley — often sheltered, often boggy, and frequently the most beautiful part of the walk.

Field boundaries tell you what to expect underfoot

The black lines criss-crossing the countryside are boundaries: walls, fences and hedgerows. The convention varies between maps, but a solid black line generally means a wall or fence, while a pecked or dotted line often means a hedge or a boundary that is less physically solid. What matters more is where your path meets them.

Hunt for the gap. A break in the boundary line, a small gate symbol, or a pair of short parallel lines usually indicates a stile, gate or crossing point. If the map shows your path meeting a wall with no gap at all, you have either misread the line or the map is out of date. Either way, plan an alternative and note it down. Then count the fields between your start and your lunch stop — six fields with gates is a relaxed morning; twelve fields of stiles is a different proposition entirely.

Notice water, woodland and the small marks

Blue is your friend. Streams, rivers, ponds and the marsh symbol — usually short horizontal blue dashes — tell you where the ground may be wet. Cross a stream where the map shows a bridge; a ford symbol means exactly what it says, and after rain it may be impassable.

Green shading shows woodland. Dense, even green is often conifer plantation, which can be dark, quiet and full of brash. Lighter, mottled green suggests broadleaf woodland, kinder underfoot and richer in birdsong. Areas of pale wash with a faint boundary are frequently open access land, where you may wander off the path altogether — a wonderful thing to know when you want to sit on a hilltop and do nothing at all.

Plan the route so the day stays gentle

Measure distance honestly. Use the map's scale — 1:25,000 or 1:50,000 — and either a strip of paper with tick marks or the edge of your thumb on the scale bar. Add a generous allowance for stiles, gates, mud and photograph stops.

• Allow roughly 4 km per hour on flat ground, less on rough or uphill terrain.
• Add around one minute for every 10 metres of ascent.
• Add a third again if the ground is boggy, overgrown or new to you.
• Plan your turnaround point before you set off, not when your legs decide for you.

Finally, mark the tricky bits. A junction where four paths meet, a path that leaves a lane through an unmarked gap, a stream crossing — write these on a small card or circle them in pencil. Note the direction of travel from the compass rose so you know whether to turn east or west. Leave a copy of your route at home, and set off knowing that the day will unfold gently, one field at a time, exactly as you planned it over that cup of tea.